HCD方式反応性イオンプレーティング法におけるチタン窒化物皮膜への不純物酸素の混入

Abstract

Attempts have been made to clarify the influence of process parameters on oxygen concentration in titanium nitride films. The films were deposited onto substrates of high speed steel, SKH51. Oxygen concentration was determined through the quantitative analysis method proposed before for electron probe microanalysis. Hardness was measured by Vickers hardness indentation at 0.098-0.49N loads. Most of the oxygen should originate from the gasses adsorbed on walls in a chamber. Higher deposition temperatures reduced the oxygen concentration because the walls were baked out on heating the substrate up to a temperature prior to deposition. Extension of depositing time also enhances the baking out, thereby making oxygen concentration decrease in the surface region of the film. The oxygen concentration decreased remarkably by applying a little bias voltage to the substrate; this may suppress the contribution of negative oxygen ions to the reaction. A decrease in nitrogen partial pressure brings about a high oxygen concentration. There was a large amount of oxygen in the film containing α-Ti. It seems that the adsorption energy of oxygen on titanium is higher than that on titanium nitride. An increase in oxygen concentration offered finer grains to TiN films, and hence their hardness increased. Precipitation of α-Ti in the films containing Ti2N causes the hardness to decrease. For single-phase α-Ti, an increase in the nitrogen+oxygen concentration gave rise to a remarkable increase in the hardness.